A real-time dynamic equivalent solution for large interconnected power systems

Dynamic equivalent has been a basic approach for analysis and computation of large scale-increasing interconnected power systems in China. Security defense of power systems and real-time monitoring of system states require more rapid and effective computation of large power grids. This paper introduces a solution for real-time dynamic equivalent of large multi-area power systems. It is based on real-time measurement data from Wide Area Measurement System and parameter identification. A parallel dynamic equivalent model composed of an equivalent generator and an equivalent synthesis load was put forward, in which the equivalent generator uses a 3rd order electromechanical transient model with damping while the equivalent synthesis load uses a static characteristic model considering both voltage and frequency. Identifiability analysis was carried out for this nonlinear dynamic equivalent model. In order to apply Laplace transformation-transfer function method, the model was firstly linearized. Particle Swarm Optimization algorithm was utilized for parameter identification of the dynamic equivalent model. For AC power systems, this model is verified on CEPRI 8-machine 36-bus example system. Load model and the style of disturbance are two remarkable factors that relate to the stability of the whole power system, which are fully considered in this paper. The simulation results show that the dynamic equivalent model can reflect the dynamic responses and the transient stability of the original system, no matter which is transient stable or unstable, angle unstable or voltage stable. When we change the load model in the original system, the static characteristic model with both voltage and frequency factors can throughout represents the dynamic behavior of the original system, which confirms its robustness of this dynamic equivalent model. All the simulation work was performed on PSASP.